Method of making iron and steel alloys



United States Patent 2,910,355 METHOD OF MAKING IRON AND STEEL ALLOYS William E. Hartman, Latrobe, Pa., assignor to Latrobe Steel Company, Latrobe, Pa., a corporation of Pennsylvania No Drawing. Application December 3, 1957 Serial No. 700,307

7 Claims. c1. 75- 133 2,910,355 Patented Oct. 27, 1959 "ice a cold charge, the recovery of molybdenum is substantially reduced.

The process of this invention may be perhaps best understood by reference to the following examples of metals made in a 5 ton electric furnace.

Example 1 16,000 pounds of steel punchings of low phosphorus scrap were added to the electric furnace hearth. 5,600 pounds of molybdenum sulfide, 1,600 pounds of lime and 400 pounds of sodium carbonate were added to the hearth with the punchings. The mass was melted down to form a molten metal bath covered with slag. Aluminum dross was added to the slag until the slag was substantially free alloys containing molybdenum by adding ferromolybdenuin, calcium molyb'date, and/or molybdenum oxide to a inolten bath. Larg'e amounts of molybdenum occur, however, as molybdenum sulfide, M08 but this material has not been considered satisfactory for direct addition to a molten iron or steel bath. When large amounts of molybdenum sulfide are used as an addition to an iron and steel bath in conventional manner the losses of molybdenum have been large and economically unfeasible and the large amounts of sulphur which remain in the bath have been considered undesirable. As a result, it has been the practice to convert molybdenum sulphide to molybdenum oxide by an oxidation process, and to then convert the thus obtained molybdenum oxide into ferromolybdenum and calcium molybdate which are then used as the furnace addition.

I have discovered a method by which molybdenum sulphide can be directly used in iron and steel melting furnaces to produce an iron and steel alloy containing a high percentage of molybdenum with substantially complete recovery of molybdenum in the metal and substantial freedom from sulphur. I have discovered that by adding molybdenum sulphide to a cold metal charge as for example, a charge of steel turnings and punchings, together with the necessary lime to form a slag and a fluidizing agent such as sodium carbonate and fluorspar, I am able to melt down the mass of cold charge and then treat the resulting slag with a reducing agent such as aluminum dross to recover substantially all of the molybdenum in the molten metal while having a very low sulphur residual in the metal. I have also found that by removing the moltent slag so formed, and back charging lime and a fiuidizing agent, such as fluorspar, onto the molten metal in the furnace to form a new slag, I am able to further reduce the sulphur to the region of .02% in the molten metal.

I have found that it is necessary to maintain the slag quite hot, preferably in the area of 3000 to 3300 F., in order to obtain the best recovery by my practice. I have found by this practice that I am able to recover about 90% of the molybdenum added even when the final molybdenum in the iron alloy is as high as 20%. I have also found that, in addition to aluminum. dross, calcium carbide, ferrosilicon and similar reducing agents will prevent the migration of not only molybdenum but also chromium and other desirable constituents from the bath to the slag.

I have also discovered that it is essential that the molybdenum sulfide be added with a cold charge. When molybdenum sulfide is added to a molten bath, with the identical composition of bath and slag as in the case of from molybdenum. Fluorspar was then added to fluidize the slag and the slag was skimmed off. Immediately thereafter 1,000 pounds of lime, and 400 pounds of sodium carbonate were backed charged onto the molten metal to form a final slag. Aluminum dross was again added to the slag along with fiuorspar to maintain the molybdenum substantially out of the slag. The bath was held until the metal had a sulfur content at the desired level.

Example 2 16,000 pounds of high speed molybdenum steel turnings were charged into an electric furnace along with 3,500 pounds of molybdenum sulfide, 1,000 pounds of lime and 400 pounds of sodium carbonate. The charge was melted down to form a molten metal bath covered with slag. This molten mass was treated as in the case of Example 1.

The recovery of molybdenum in the foregoing two examples was about of the charged molybdenum.

I have successfully made molybdenum containing alloys with as much as 30% molybdenum by the practices outlined herein.

The process of the invention may be used to produce in iron and steel alloys of molybdenum, of a great variety of compositions. It may be used to produce molybdenum alloy steels of conventional analysis for forging, casting, rolling or any other purpose or it may be used to produce high molybdenum iron or steel for use as additive alloys.

While certain preferred practices of this invention have been described herein above, it will be understood that this invention may be otherwise embodied with the scope of the following claims.

I claim:

1. The method of making molybdenum containing iron and steel alloys from molybdenum sulfide comprising the steps of adding molybdenum sulfide to a cold solid charge of ferrous material and sufficient lime to form a slag, heating said solid materials to fusion to form a molten metal mass covered with slag, adding a reducing agent to the molten mass sufficient to maintain the slag substantially free of molybdenum and separating the slag and the molten metal.

2. The method of making molybdenum containing iron and steel alloys from molybdenum sulfide comprising the steps of adding molybdenum sulfide to a cold solid charge of ferrous material and sufiicient lime to form a slag in an electric furnace, heating said solid materials to form a molten metal mass having a temperature in excess of 3000 F., adding a reducing agent to the molten mass sufiicient to maintain the slag substantially free of molybdenum and separating the slag and the molten metal.

3. The method of making molybdenum containing iron and steel alloys from molybdenum sulfide comprising the steps of adding molybdenum sulfide to a cold solid charge of ferrous material, suflicient lime to form a slag and sufficient material from the group consisting of fluorspar, sodium fluoride and sodium carbonate to impart fluidity to the slag, heating said solid materials to form a molten metal mass, adding a reducing agent selected "from the group consisting of aluminum, and calcium carbide to the molten mass suflicient to maintain the'slag 1' substantially free of molybdenum and separating the slag and the molten metal. p

4. The method of making'molybdenum containing iron 7 and steel alloys from molybdenum sulfide comprising thesteps of adding molybdenum sulfide to a cold solid charge of iron and steel scrap sufficient lime and fluorspar to form a fluid slag, heating said solid material to form molten mass sufiicient to maintain the slag substantially a molten metal mass, adding aluminum dross to the molten mass suflicient to maintainthe slag substantially free of molybdenum and separating the slag and the molten metal.

'5. The method of making molybdenum containing iron Y and steel alloys from molybdenum sulfide comprising the steps of adding molybdenum sulfide to a cold solid charge of ferrous material and sufficient lime to form a slag, heating said solid materials to form a molten metal mass, adding a reducing agent to the molten mass sufficient to maintain the slag substantially free of molybdenum removing the slag from the molten metal, immediately adding sufficient lime to form a second slag on the metal, adding a reducing agent to the second slag to maintain said slag substantially free of molybdenum, holding the slag and metal in contact until substantially all of the sulfur has migrated to the slag and separating the slag and molten metal.

6. The method as claimed in claim 5, wherein the reducing agent is aluminum dross.

7. The method of making molybdenum containing iron and steel alloys from molybdenum sulfide comprising the steps of adding molybdenum sulfide to a cold solid charge of ferrous material, suflicient lime to form a slag and suflicient material from the group consisting of fluor- .-spar, sodium fluoride and sodium carbonate to impart fluidity to the slag, heating said solid material to form a molten metal mass, adding aluminum dross to the References Cited in the file of this patent' UNITED STATES PATENTS 1,613,571 Becket Jan. 4,192.7

1,797,728 McIntosh Mar. 24, 1931 FOREIGN PATENTS V 184,912 Great Britain Aug. 31, 1922 

1. THE METHOD OF MAKING MOLYBDENUM CONTAINING IRON AND STEEL ALLOYS FROM MOLYBDENUM SULFIDE COMPRISING THE STEPS OF ADDING MOLYBDENUM SULFIDE TO A COLD SOLID CHARGE OF FERROUS MATERIAL AND SUFFICIENT LIME TO FORM A SLAG, HEATING SAID SOLID MATERIALS TO FUSION TO FORM A MOLTEN METAL MASS COVERED WITH SLAG, ADDING A REDUCING AGENT TO THE MOLTEN MASS SUFFICIENT TO MAINTAIN THE SLAG SUBSTANTIALLY FREE OF MOLYBDENUM AND SEPARATING THE SLAG AND THE MOLTEN METAL. 